lost 12VDC in coach

When mine did that it was the 200 amp fuse

When I lost power, took me some time with help, to find- hidden under dashboard- 40A breaker.

There often is an automatic circuit breaker between the battery bank and the 12 dc distribution center. It may have failed.

My first tool choice is a 12 volt automotive test light

Brigth = Good
Dark = bad
Dim also bad
Problem exists between Bright and Not Bright

Start with clip any non-painted metal part near battery tip to battery Positive Bright good. Move out along the positive wire to the other end of the wire connected to the battery... Same test. .NOTE.. when you move the ground clip. if possible re-test the last known good spot (Testing ground)

No light on the first test move ground clip to battery - If bright bad ground cable

You come to a box with 2 bolts and wires attached. test all HEAVY wires if there are both heavy and small wires that is your cut off solenoid.

Or, it could be a bad ground.

Sounds like your AC to DC converter has a problem.
Need to check to see if AC (120v) is getting to one side of converter,
and if so, check to see if DC (12v) is getting out of he other side.

Usually there is a in-line fuse after the battery. Mine was hidden. Follow the 12V line. Should be with-in 2-3 feet of the battery. Also, if you have a shut off switch check to see if that is on. It might have been moved.

get your volt meter out start at the battery.

How long have you had this coach?
Does it have a "Salesman Switch near the door?
Start checking from the house battery to the fuse panel.

Matt